1. Field of the Invention
The present invention relates to a subminiature imaging optical system, and more particularly, to a subminiature imaging optical system installed in a mobile communication terminal and a personal digital assistant (PDA) or utilized in a surveillance camera and a digital camera.
2. Description of the Related Art
In general, mobile communication terminals had only functions of basic communication at their incipient stage. However, with increased use, the mobile communication terminals are required to have diversified functions ranging from photographing to image transmission and video communication, continuously evolving in their functions and services. Recently, a new expanded concept of mobile communication terminal by integrating digital camera technology with mobile phone technology, i.e., so called camera phones or camera mobile phones are significantly attracting attention. Further, a digital camcorder technology has been integrated with a mobile phone technology to develop a camcorder mobile phone or camcorder phone capable of storing and transmitting a live image running for several minutes or more.
Of late, a camera installed on the mobile phone should perform like an electronic still camera, while being required to be miniaturized, light-weight and low-cost. An image sensor such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) is reduced in pixel size thereof but increased in size itself. Thus, the imaging optical system employing such an image sensor needs to be high in resolution.
In order to satisfy miniaturization and low cost, the imaging optical system mounted on a camera of a mobile phone and a personal computer needs to have lenses of as small a number as possible, but this restricts a degree of freedom in designing and undermines the optical capabilities.
Therefore, there is required an imaging optical system which can be subminiaturized while achieving high resolution.